Many specialized types of seating furniture benefit from adjustability of their parts to conform to the particular size of the individual sitting on such furniture. Components of adjustable office chairs are usually adjusted by a knob which controls a frictional clamping relationship between a first member and a second member. Such measures work well enough in most circumstances. However, with the growing effort to employ disabled persons, there arise situations where a worker is unable to satisfactorily adjust an otherwise serviceable chair because of the level of physical strength required. Therefore, a chair adjustment mechanism which has a high "mechanical advantage" would be useful to facilitate the use of such chairs by all types of workers.
Chairs adapted for professions such as dentistry, certain kinds of medicine, barbering, cosmetology, and other fields have employed geared and powered mechanisms for adjusting the various components thereof. Such mechanisms are usually built heavily for increased durability. The mechanisms are also generally complex, relatively large, and expensive, as are the chairs. Such professional chairs are usually fixed, that is, connected to a floor. Office chairs, on the other hand, are usually mobile, having casters thereon, for greater flexibility of use. Improvements in the adjustment mechanisms of office chairs should not increase their weight significantly, particularly if such chairs are to be used by the disabled. In addition, such improvements should not increase the expense of such office chairs significantly or there is decreased incentive to procure such equipment. The chair adjustment mechanisms which are known in the field of professional type chairs are not necessarily directly applicable to relatively economical, light office chairs because of the weight, size, and expense of such mechanisms.